Scientists have produced a rare form of quantum matter known as a Bose-Einstein condensate (BEC) using molecules instead of atoms.
Made of chilled sodium-cesium molecules, these BECs are as cold as five nanokelvins, or about -459.66 °F, and remain stable for a remarkable two seconds.
“These molecular BECs open up new research arenas, from understanding truly fundamental physics to advancing powerful quantum simulations,” noted Columbia University physicist Sebastian Will. “We’ve reached an exciting milestone, but this is just the beginning.”
Understanding the Bose-Einstein Condensate (BEC)
A Bose-Einstein condensate (BEC) is a state of matter that occurs when a collection of bosons, particles that follow Bose-Einstein statistics, are cooled to temperatures very close to absolute zero.
Under such extreme conditions, a significant fraction of bosons occupy the lowest quantum state, leading to macroscopic quantum phenomena.
This means that they behave as a single quantum unit, effectively “collapsing” into a single wave function that can be easily described using the principles of quantum mechanics.
The fascinating aspect of BECs stems from their superfluid properties—exhibiting zero viscosity while flowing, allowing them to move without dissipating energy.
This unique property allows BECs to simulate other quantum systems and explore new areas of physics.
For example, studying BECs can provide insights into quantum coherence, phase transitions, and many-body interactions in quantum gases.
The creation of molecular BECs, such as those involving sodium-cesium molecules, extends this research even further, potentially leading to breakthroughs in quantum computing and precision measurements.
Ultracold BEC odyssey
The journey of BECs is long and winding, dating back a century to the works of physicists Satyendra Nath Bose and Albert Einstein.
They prophesied that a cluster of particles cooled to the brink of stasis would coalesce into a single macroentity governed by the dictates of quantum mechanics. The first true atomic BECs appeared in 1995, 70 years after the original theoretical predictions.
Atomic BECs have always been relatively simple—round objects with minimal polarity-based interactions. But the scientific community began to crave a more complex version of BECs made up of molecules, albeit to no avail.
Finally, in 2008, the first breakthrough came when a duo of physicists cooled a gas of potassium rubidium molecules to about 350 nanokelvins. The drive to achieve an even lower temperature to pass the BEC threshold continued.
Microwaves: the cooling solution
In 2023, the initial step toward this goal was achieved when the research team created the desired ultracold sodium-cesium molecular gas using a combination of laser cooling and magnetic manipulation. To further reduce the temperature, they decided to introduce microwaves.
Microwaves can build small shields around each molecule, preventing them from colliding and causing the overall temperature of the sample to drop.
Propulsion in the age of quantum control
The group’s achievement of creating a molecular BEC represents a spectacular achievement in quantum control technology.
This brilliant work of science is destined to influence numerous scientific fields, from the study of quantum chemistry to the study of complex quantum materials.
“We really have a deep understanding of the interactions in this system, which is vital for next steps, such as studying many-body dipolar physics,” said co-author and Columbia postdoc Ian Stevenson.
The research team developed interaction control schemes, tested them from a theoretical angle and executed them in the real experiment. It’s truly amazing to witness these microwave “shielding” concepts come to fruition in the lab.
Unfolding a new canvas in quantum physics
The creation of molecular BECs enables the fulfillment of many theoretical predictions. The stable nature of these molecular BECs allows for an in-depth study of quantum physics.
A proposal to construct artificial crystals with BECs held in a laser-made optical lattice can provide a complete simulation of the interactions in natural crystals.
In moving from a three-dimensional system to a two-dimensional one, new physics is expected to emerge. This area of research opens up many possibilities in the study of quantum phenomena, including superconductivity and superfluidity, among others.
“It feels like a whole new universe of possibilities is opening up,” concluded Sebastian Will, summing up the enthusiasm in the scientific community.
BEC: From Atoms to Molecules
In summary, this study describes the successful creation of a Bose-Einstein condensate (BEC) using ultracold sodium-cesium molecules, reaching a steady state at five nanokelvins in two seconds.
Using a combination of laser cooling, magnetic manipulation, and innovative microwave shielding, the research group and their theoretical collaborator achieved unprecedented control over molecular interactions at quantum levels.
This milestone enables a comprehensive study of quantum phenomena such as coherence, phase transitions and many-body interactions, potentially unlocking new avenues in quantum simulations, quantum computing and precision measurements.
The full study is published in the journal Nature.
Special thanks to Ellen Neff of Columbia University.
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